Mars: Landing Site Geology, Mineralogy and Geochemistry 337
FIGURE 6 TheViking 1landing site. (a) Mosaic of theViking 1landing site showing bright drifts
and dark rocks. Large rock to left is Big Joe and is subrounded. Smaller angular dark rocks are sitting
on soil and have been interpreted as impact ejecta blocks. Bright drift in the center of the image
shows layers, and some particles may be large enough to require deposition by running water rather
than the wind. (b) Color mosaic of theViking 1landing site showing dusty reddish surface, darker
pitted rocks nearby, and a crater rim on the left horizon. Jointed slightly lighter toned low rock mass
in the middle distance appears to be outcrop. The location of the site on ridged plains suggests that
the outcrop is basalt, with angular rocks as ejecta and drift materials deposited by either the wind or
floodwaters from Maja or Kasei Valles.
high thermal inertia, high rock abundance (18%), slightly
lower albedo, and relation to an analogous catastrophic out-
flow depositional plain in the Channel Scabland. All of these
predictions were confirmed by data gathered by theMars
Pathfinderlander and rover (Fig. 8). TheSpiritlanding site
in Gusev crater has comparable thermal inertia and fine
component thermal inertia and albedo to the twoViking
sites and so was expected to be similar to these locations,
but with fewer rocks (8%). Dark dust devil tracks in or-
bital images suggested some of the surfaces would be lower
albedo, where the dust has been preferentially removed
(Fig. 9).Spirithas landed and traversed across both dusty
(Fig. 10) and dust devil track surfaces and found that the
average rock abundance is similar to expectations, that in
darker dust devil tracks the albedo is low and the surface
is relatively dust free (at the landing site), and that in ar-
eas outside of dust devil tracks the albedo is higher and
the surface is more heavily coated with bright atmospheric
dust that has fallen from the sky (Fig. 10). The Meridiani
Planum site has moderate thermal inertia, very low albedo
and few rocks. This site was expected to look very different
from the three landing sites with a dark surface, little bright
red dust, and few rocks.Opportunityhas traversed across
a dark, basaltic sand surface with very few rocks and almost
no dust (Fig. 11).
The slopes and relief at various length scales that were
important to landing safely were also estimated at the five
landing sites using a variety of altimetric, stereo, shape
from shading, and radar backscatter remote sensing meth-
ods. Results estimated from these data are in accord with
what was found at the surface. Of the five landing sites,
Meridiani Planum was judged to be the smoothest, flattest
location ever investigated at 1 km, 100 m, and several me-
ter length scales, which is in agreement with the incredibly
smooth flat plain traversed byOpportunity(Fig. 11). On
the other extreme, theMars Pathfinderlanding site (Fig. 8)